linux-kernel - Re: [PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup

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Message-ID: <20250630152952.GG24861@pendragon.ideasonboard.com>
Date: Mon, 30 Jun 2025 18:29:52 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: Desnes Nunes <desnesn@...hat.com>, hansg@...nel.org,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

On Mon, Jun 30, 2025 at 05:15:38PM +0200, Ricardo Ribalda wrote:
> Hi Desdes
> 
> How did you trigger this build warning? I believe we use C11
> 
> https://www.kernel.org/doc/html/latest/process/programming-language.html

Note that the local declaration of the loop counter shadows the global
one. I would have expected a different compiler warning though.

The shadowing was introduced by

commit 10acb9101355484c3e4f2625003cd1b6c203cfe4
Author: Ricardo Ribalda <ribalda@...omium.org>
Date:   Thu Mar 27 21:05:29 2025 +0000

    media: uvcvideo: Increase/decrease the PM counter per IOCTL

and I think it should be fixed (while at it, with an unsigned int local
loop counter instead of a signed int) as it's not a good practice.

> On Mon, 30 Jun 2025 at 17:07, Desnes Nunes <desnesn@...hat.com> wrote:
> >
> > This fixes the following compilation failure: "error: ‘for’ loop
> > initial declarations are only allowed in C99 or C11 mode"
> >
> > Cc: stable@...r.kernel.org
> > Fixes: 221cd51efe45 ("media: uvcvideo: Remove dangling pointers")
> > Signed-off-by: Desnes Nunes <desnesn@...hat.com>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 44b6513c5264..532615d8484b 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -3260,7 +3260,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
> >  void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >  {
> >         struct uvc_entity *entity;
> > -       int i;
> > +       unsigned int i;
> >
> >         guard(mutex)(&handle->chain->ctrl_mutex);
> >
> > @@ -3268,7 +3268,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >                 return;
> >
> >         list_for_each_entry(entity, &handle->chain->dev->entities, list) {
> > -               for (unsigned int i = 0; i < entity->ncontrols; ++i) {
> > +               for (i = 0; i < entity->ncontrols; ++i) {
> >                         if (entity->controls[i].handle != handle)
> >                                 continue;
> >                         uvc_ctrl_set_handle(handle, &entity->controls[i], NULL);

-- 
Regards,

Laurent Pinchart